getting an old Nexus 7 to connect to wifi

I have an old 2012 Asus Nexus 7. How can I get it to connect to wifi again? My goal is to use it as a digital photo frame, where the software for showing the slideshow of photos is a React app (website) that I've built. So all I need this tablet to be able to do is browse a website hosted on my LAN. (Ideally the browser ideally will support localStorage and IndexedDB.) Currently, I can't get the Nexus 7 to connect to my wifi. It has some custom limited version of Android 7.1.2 that I barely remember installing. Sometimes it can see my wifi networks and lets me enter its password, but then never lets me browse the internet. Sometimes the wifi is "Off", and when I try to turn it "On", it just hangs. My WiFi router is a NOKIA BGW320-505 (AT&T fiber) with WPA-2, WPA-3, and B/G/N/AX. NOKIA BGW320-505 gives me 3 options in the dropdown for WPA Version: "WPA-1 and WPA-2", "WPA-2", "WPA-2 and WPA-3". It has been on "WPA-2 and WPA-3", and I'd love to keep it there. I temporarily changed it to WPA-2, and even then the Nexus won't connect. I've already tried a factory reset of the Nexus. What are my options for solving this? I'd be up for installing a new OS on the Nexus if there is a high chance of achieving my goal.